FIELD OF THE INVENTION
The present invention relates to an apparatus for controlling a suspension system disposed between a wheel and the body of an automotive vehicle, and more particularly to such an apparatus being provided with means for adjusting a response of the suspension system to mechanical excitations transmitted by the wheels and/or the body.
Conventionally, a suspension system includes a spring and a shock absorber, which are disposed in parallel between a suspended mass, that is the vehicle body, and a mass constituted by a wheel equipped with a tire and its suspension arm, which is excited by irregularities in the surface on which the vehicle travels. The role of the shock absorber is to absorb the energy stored in that system of masses and elastic devices in order to prevent that energy from causing oscillation of the body that is detrimental to the comfort of the passengers, and oscillation of the wheels that is detrimental to the wheel/ground contact and therefore to the safety of the passengers.
Such a system has two resonant frequencies, which are currently located in the band from 1 to 2 Hz for the body and the band from 10 to 15 Hz for the wheel and its suspension arm. French Patent Application No. 92 01450, filed Feb. 10, 1992 by the present applicant, describes a method for controlling the shock absorption coefficient of the shock absorber of a suspension system, which is embodied in such a way as not to degrade the filtering capacity of the system for frequencies other than the aforementioned resonant frequencies. However, that method is still of the type that employs a single control strategy, which is unique to the shock absorber, and entails a compromise between the two dynamics of the suspension system, which are characterized by the aforementioned two resonant frequencies. Therefore, control strategies that are as flexible as desired, which are embodied by a set of rules, such as "if the vehicle speed is high, then vehicle safety is overriding", cannot be employed.